Purger

“The Goo evolving beyond its programming is not entirely unexpected. When the program is active, size restrictions were enforced for fear of emergent behaviors. Since being abandoned, these fears have been manifested in what we are calling the "Purger", the largest single mass of protean goo. The Purger is not only capable of consuming everything in its path, but also subverting the ground beneath us, undermining our defenses and obliterating our forces. The Purger is truly a force of nature, and appropriately named.”— Singleton[1]

Considered to be the largest single concentration of Goo known to exist. Only the largest of Mother Goo can begin the transformation into a Purger. Combining with other Mothers or Formless Goo accelerates the transformation.[2]